Toy building block



FIG. 1 is a perspective view of a toy building block showing my new design;

FIG. 2 is a side elevational view thereof; the side opposite being a mirror image;

FIG. 3 is a front elevational view thereof; the side opposite being a mirror image, and

FIG. 4 is a top plan view thereof; the side opposite being identical. 

The ornamental design for a toy building block, as shown and described. 